1. Field of the Invention
The present invention relates to a reflector mounting structure used for a projection display device or the like and a projection display device using the reflector mounting structure.
2. Description of the Related Art
A mirror (reflector) having a reflecting surface is mounted on a projection display device such as a projector. However, to project an image without distortion, the mirror needs to be mounted with a high position accuracy. Conventionally, therefore, the mirror is fixed on a fixing member provided in the projection display device by a number of screws. However, when the mirror expands or contracts due to a change in temperature or humidity, a stress is accumulated in the mirror, originating at screwed parts. The shape of the reflecting surface of the mirror is then deformed due to the stress, and as a result, there is a problem that distortion is generated on an image projected on a screen.
To solve this problem, for example, Japanese Patent No. 3913265 (paragraphs 0017 to 0020, FIGS. 1 and 5) discloses the following reflector holding mechanism. That is, in this conventional reflector holding mechanism, a first lug is provided below a mirror, and second lugs are respectively provided at two positions on the right and left sides of an upper part of the mirror. The first lug is supported by a pivot supporting unit provided in a fixing member and the second lug is supported by a pair of right and left slide supporting units provided in the fixing member, thereby holding the mirror by the fixing member. With this structure, even when temperature and humidity change, positions of the second lugs provided at two positions on the right and left move, and the mirror expands or contract as a result. Accordingly, deformation of the mirror is alleviated and distortion of an image is also alleviated.
However, in the conventional reflector holding mechanism described above, when the shape of the mirror changes due to a change in temperature or humidity, or due to an impact applied at the time of transport, the following problem is caused. That is, when the temperature or humidity returns to its original state, or when the mirror tries to be its original shape immediately after the impact, the mirror does not slide smoothly or even if it slides in the slide supporting unit, it is hard to return to its original position due to a friction between the second lugs provided on the sides of the mirror and the fixing member. Therefore, there is a problem that deformation of the mirror is not recovered and image distortion occurs as a result.